Lesson 4: Configuring IP Networks

IP Address

At the TCP/IP Internet layer (the OSI Network layer), an _______ is used to identify each host. The _______ provides two pieces of information. The network number (network ID) and the host number (host ID).

Packet Too Big

Class of error added with ICMPv6 for IPv6. Under IPv6, routers are no longer responsible for packet fragmentation and reassembly, so the host must ensure that they fit in the MTUs of the various links used.

Tracert

Command used to investigate the route being taken.

Customer premises equipment (CPE)

DHCPv6 Prefix Delegation (PD) is used by ISPs to provide routable address prefixes to a SOHO router, installed as____________________. With PD, the ____ router obtains a prefix from a delegating router, installed upstream on the ISP's network. The ____ router then uses the prefix to assign devices on the customer's network with IPv6 addressing information by using router advertisements or DHCPv6, or both.

Routing table

Discovered routes are held in a ___________________.

Address autoconfiguration

Enables a host to configure IPv6 addresses for its interfaces automatically and detect whether an address is already in use on the local network, by using neighbor solicitation (NS) and neighbor advertisement (NA) messages.

Prefix discovery

Enables a host to discover the known network prefixes that have been allocated to the local segment. This also allows next-hop determination (whether a packet should be addressed to a local host or a router). __________ uses router solicitation (RS) and router advertisement (RA) messages. An RA contains information about the network prefix(es) served by the router, information about autoconfiguration options, plus information about link parameters, such as the MTU and hop limit. Routers send RAs periodically and in response to a router solicitation initiated by the host.

Packets

Encapsulate data from the Transport layer, adding several fields as a header.

Class C

In this class of network addresses there are over 2 million networks but support only 254 hosts. Class identified from the first octet of the IP address in decimal ranges from 192-223. All networks start with a binary 110.

IPv4 Address

Is 32 bits long and is used within an IP packet to define the source and destination of the packet.

w.x.y.z

Is a dotted decimal IPv4 address.

Base 16 (Hexadecimal)

Is a more convenient way of referring to the long sequences of bytes used in IPv6. The possible values of each digit represented by the numerals 0 through 9 and the characters A, B, C, D, E, and F. every ___ digit lines up neatly with four binary digits (a nibble), so conversion is a straightforward matter of dividing the binary digits into groups of four, then converting each group individually.

Default gateway

Is the IP address of a router on the same IP network as the host. Messages destined for other IP networks are sent to the ______________ address by the source host.

4to6

It is also possible to tunnel IPv4 through an IPv6 network, in which case the process is known as _______ tunneling, as defined in RFC 2473. However, given that the most likely transit network for tunneling between sites is the Internet, which is based on IPv4, this type of tunnel is currently of limited use.

Teredo

Microsoft provides support for _________ tunneling by Windows hosts. ________ tunnels IPv6 packets as IPv4-based UDP messages over port 3544. Using UDP rather than TCP allows tunneling through NAT devices.

Internet protocol

Provides logical hosts in network addressing and routing.

Octets

The 32 bits are subdivided into four groups of 8 bits (1 byte) known as ______.

ping

The ________ utility sends a configurable number and size of ICMP packets to a destination host. This can be used to perform a basic connectivity test that is not dependent on the target host running any higher-level applications or services.

255.255.0.0

The default subnet masks correspond to the three classes of unicast IP address (A, B, and C). The default masks comprise whole octets: Class B is ______________.

255.255.255.0

The default subnet masks correspond to the three classes of unicast IP address (A, B, and C). The default masks comprise whole octets: Class C is _____________.

Broadcast

The destination address is one specially configured to be delivered to all hosts on the local network.

2^n-2

The number of hosts per subnet can be expressed using the formula _____, where n is the number of bits you have allocated for the host ID. 12 bits is enough for 4094 hosts in each subnet. **You subtract 2 because each subnet's network address and broadcast address cannot be assigned to hosts.

Class E

This class of network addresses are reserved for experimental use and testing. (240.0.0.0 through 255.255.255.255)

Class D

This class of network addresses are used for multicasting. (224.0.0.0 through 239.255.255.255)

Class A

This class of network addresses supports large numbers of hosts, over 16 million. However, there are only 126 _____ network addresses. Class identified from the first octet of the IP address in decimal ranges from 1-126. All networks start with a binary 0.

ipconfig

This command is used to verify the IP configuration on Windows-based systems. Without any switches the command will display the IP address, subnet mask, and default gateway (router) for all network interfaces to which TCP/IP is bound.

Variable length subnet masking (VLSM)

This complementary technique allows a network designer to allocate ranges of IP addresses to subnets that match the predicted need for numbers of subnets and hosts per subnet more closely. The LAN's internal routers use the /24 prefix or even multiple prefixes to create subnets of different sizes.

ipconfig /flushdns

This ipconfig command clears the DNS resolver cache.

ipconfig /all

This ipconfig command displays complete TCP/IP configuration parameters for each interface to which TCP/IP is bound, including whether the Dynamic Host Configuration Protocol (DHCP) is enabled for the interface and the interface's hardware (MAC) address.

ipconfig /displaydns

This ipconfig command displays the Domain Name System (DNS) resolver cache.

ipconfig /renew interface

This ipconfig command forces a DHCP client to renew the lease it has for an IP address.

Ipconfig /registerdns

This ipconfig command registers the host with a DNS server (if it supports dynamic updates).

ipconfig /release interface

This ipconfig command releases the IP address obtained from a DHCP Server so that the interface(s) will no longer have an IP address.

Dotted decimal notation

This notation requires each octet to be converted to a decimal value. The decimal numbers are separated using a period.

Host number (Host ID)

This number identifies a host within an IP network.

Network number (network ID)

This number is common to all hosts on the same IP network.

DHCP relay agent

To contact a DHCP server, each broadcast domain must be served by its own DHCP server. On a large network, this would mean provisioning and configuring many DHCP servers. To avoid this scenario, a ___________ can be configured to provide forwarding of DHCP traffic between subnets. Routers that can provide this type of forwarding are described as RFC 1542 compliant.

Redirect

Type of ICMP message. Most hosts channel all remote communications through the default gateway. If there are in fact multiple routers and a more efficient route can be identified, the default gateway can send a redirect message to the host to update its routing table. The router still delivers the original message.

Destination unreachable

Type of ICMP message. This class of message indicates that a local host or a host on a remote network (or a protocol or port on a host) cannot be contacted. This might be caused by some sort of configuration error or by a host or router not being available.

Unicast

When an IPv4 host wants to send a packet to a single recipient it is addressed to the IP address of the destination host.

Network Address Translation (NAT)

a router configured with a single or block of valid public IP addresses; the router translates between the private and public addresses using a process called _____________.

Multicast Listener Discovery (MLD)

allows nodes to join a multicast group and discover whether members of a group are present on a local subnet. _______ is defined in RFC 3810.

Base 2 (binary)

digits can take one of two different values (0 and 1). The place values are powers of 2 (21=2, 22=4, 23=8, 24=16, and so on).

Dual-stack

hosts can run both IPv4 and IPv6 simultaneously and communicate with devices configured with either type of address. Most modern desktop and server operating systems implement _______ IP.

MAC reservation

is a mapping of a MAC address to a specific IP address within the DHCP server's address pool. When the DHCP server receives a request from the given MAC address, it always provides the same IP address. This is also referred to as static or fixed address assignment.

Classless Inter-Domain Routing (CIDR)

is described in RFC 4632. Essentially, it uses bits normally assigned to the network ID to mask the complexity of the subnet and host addressing scheme within that network. ______ is also sometimes described as supernetting.

Time to Live (TTL)

is nominally the number of seconds of packing and stay on the network before being discarded; otherwise packets could endlessly loop around and Internet.

Subnetting

is the process of logically dividing a network into smaller subnetworks (subnets), with each having a unique address.

Internet Group Management Protocol (IGMP)

is typically used to configure group memberships and IP addresses.

Generic Routing Encapsulation (GRE/47)

is used to tunnel packets across an intermediate network. This is used (for example) in some virtual private network (VPN) implementations.

Internet Group Messaging Protocol (IGMP/2)

is used with multicasting.

Automatic allocation

refers to an address that is leased permanently to a client. This is distinct from static allocation as the administrator does not pre-determine which IP address will be leased.

Bootstrap Protocol (BOOTP)

was developed as a means of supplying a full set of configuration parameters—IP address, subnet mask, default gateway, DNS server addresses, and so on—to a host. is still used in some circumstances to provide addressing information to diskless workstations and print devices. The main drawback of __________ is that it depends on a static configuration file mapping IP addresses to MAC addresses.

Scope

A ________ is a region of the network. IPv6 unicast addressing is ______d.

Miredo

A compatible open source implementation of Teredo, known as _________, is available for UNIX/Linux operating systems.

DHCP options

Additional IP-related settings outside the IP address and subnet mask provided to a client. May include The default gateway, the IP address(es) of DNS servers, the DNS suffix (domain name) to be used by the client.

Static IP addressing

All parameters required by TCP/IP were configured manually. Each host must be allocated an appropriate IP address and subnet mask, plus the IP address of the default gateway (router) for its network.

Classful addressing

Allocates a network ID based on the first octet of the IP address. Was employed in the 1980s, before the use of subnet masks to identify the network ID portion of an address was developed.

Echo request/reply

Type of ICMP message. These are used for testing a connection with the ping utility. If a request message reaches the destination host, it generates a reply and sends it back to the source. If the request message does not reach its destination, an appropriate error message is generated.

Time exceeded

Type of ICMP message. This is used when the Time to Live (TTL) of a packet reaches 0. The TTL field in a packet has a maximum value of 255, and this value is reduced by one every time the packet crosses a router. The TTL is eventually reduced to 0 if the packet is looping (because of a corrupted routing table) or when congestion causes considerable delays. The router then discards the packet and a warning packet is sent back to the source host.

Private addressing

Typically used by Hosts communicating with one another over a local area network (LAN). The IP addresses can be drawn from one of the pools of addresses defined in RFC 1918 as non-routable over the Internet. Class A address range is 10.0.0.0 to 10.255.255.255. Class B address range is 172.16.0.0 to 172.31.255.255. Class C address range is 192.168.0.0 to 192.168.255.255.

ifconfig

UNIX and Linux hosts provide this command, which provides similar output to the Windows ipconfig program.

Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)

Under ________, a dual-stack router takes an IPv6 packet and rewrites it as an IPv4 packet. The ______________ router allows for a network with mixed IPv4 and IPv6 hosts, but it cannot be used for routing between networks.

Generic Routing Encapsulation (GRE)

Was developed by Cisco and is supported by many Linux distributions and by Microsoft since Windows Server 2012 R2 (with hotfixes). ________ allows a wide variety of Network layer protocols to be encapsulated inside virtual point-to-point links. This protocol has the advantage that because it was originally designed for IPv4, it is considered a mature mechanism and can carry both v4 and v6 packets over an IPv4 network.

Public addressing

An IP network or host address is one that can establish a connection with other public IP networks and hosts over the Internet. The allocation of public IP addresses is governed by IANA and administered by regional registries and Internet Service Providers (ISPs).

Unique local addressing (ULA)

Assigns addresses that are only routable within a site (or collection of sites). Is designed for hosts that will never access the Internet.

Protocol field

Describes what is contained (encapsulated) in the payload so that the receiving host knows how to process it. For most packets, the value will indicate a Transmission Control Protocol (TCP/6) segment or a User Datagram Protocol (UDP/17) datagram.

Broadcast domain

A _____________ is one where all the hosts receive the same broadcast packets. _________ boundaries are established at the Network layer (layer 3) by routers. Routers do not forward broadcasts, except in some specially configured circumstances. Consequently, each IP network is a separate ________. The last address in any IP network is the broadcast address, or put another way, the address in any IP network where all the host bits are set to 1.

Multicast

A destination address which represents a group of computers, programmed to respond to a particular address.

Base 10 (decimal)

A digit can take any one of ten different values (0 through 9), and the values of the different place positions within a number, moving from right to left, are units (ones), tens, hundreds, thousands, and so on.

Router advertisement (RA)

An RA contains information about the network prefix(es) served by the router, information about autoconfiguration options, plus information about link parameters, such as the MTU and hop limit. Routers send ___________s periodically and in response to a router solicitation initiated by the host.

IPv4 mapped address

An __________ is expressed ::ffff:192.168.0.1 (that is, 80 0s followed by 16 1s and then the 32-bit IPv4 address, expressed by convention in dotted decimal). This sort of address is never assigned to hosts, but it is used by IPv4/IPv6 routers to forward traffic between IPv4 and IPv6 networks.

Tunneling

As an alternative to dual-stack routing, _________ can be used to deliver IPv6 packets across the IPv4 Internet.

Lease time

Determines how long the client will maintain its IP address. A long period means the client does not have to renew the lease as frequently, but the DHCP server's pool of IP addresses is not replenished. Where IP addresses are in short supply, a short period enables the DHCP server to allocate addresses from computers that are not in use.

Interface identified

Determines the interface ID of an IPv6 address by utilizing the MAC address. As a MAC address is currently 48 bits (6 bytes), a (relatively) simple translation mechanism allows driver software to create a 64-bit interface ID (an EUI-64) from these 48 bits.

Flag

Due to limitations in the underlying network, IP may fragment the packet into more manageable pieces. IP assigns a new header to each fragment containing: A _________ to indicate whether more fragments follow.

Fragment identifier

Due to limitations in the underlying network, IP may fragment the packet into more manageable pieces. IP assigns a new header to each fragment containing: A __________ to help group fragments together.

Offset

Due to limitations in the underlying network, IP may fragment the packet into more manageable pieces. IP assigns a new header to each fragment containing: An __________ to assist the destination host in reconstructing the fragments into the original packet.

ip

Going forward, the ____ command is intended to replace ifconfig. It is a more powerful tool, with options for managing routes as well as the local interface configuration.

Neighbor Discovery (ND)

IP address resolution to a specific hardware interface in IPv6. This protocol replaces ARP in IPv4.

Stateless address autoconfiguration (SLAAC)

IPv6 uses a more flexible system than IPv4 for address autoconfiguration. The host generates a link-local address and tests that it is unique by using the Neighbor Discovery (ND) protocol. The host listens for a router advertisement (RA) or transmits a router solicitation (RS) using ND protocol messaging. Routers send out advertisements periodically and will respond to a solicitation request to enable clients to determine in which network they reside. The router can either provide a network prefix, direct the host to a DHCPv6 server to perform stateful autoconfiguration, or perform some combination of stateless and stateful configuration.

6to4

In _____ automatic tunneling (RFC 3056), no host configuration is necessary to enable the tunnel. ______ addresses start with a leading 2002. Essentially, when ______ is implemented, the IPv6 packets are inserted into IPv4 packets and routed over the IPv4 network to their destination. Routing decisions are based on the IPv4 address until the packets approach their destinations, at which point the IPv6 packets are stripped from their IPv4 carrier packets and forwarded according to IPv6 routing rules. Supports only public IPv4 addresses.

Class B

In this class of network addresses there are 16 thousand networks, each containing up to 65,000 hosts. Class identified from the first octet of the IP address in decimal ranges from 128-191. All networks start with a binary 10.

Address pool

Is the range of IP addresses that a DHCP server can allocate to clients on a particular subnet. To define an ________, you must provide a start and end IP address along with a subnet mask. The subnet mask given must be such that the entire range of addresses is contained within the scope of a single subnet.

Internet Control Message Protocol (ICMP/1)

Is used for status messaging and connectivity testing.

Subnet mask (netmask)

Is used to distinguish Network ID and Host ID within a single IP address. It is used to "mask" the host ID portion of the IP address and thereby reveal the network ID portion.

Differentiated Services Code Point (DSCP)

Is used to indicate a priority value for the packet. This can be used with class of service (CoS) and quality of service (QoS) mechanisms to facilitate better quality real-time data transfers, such as video streaming or Voice over IP calling.

Internet Control Message Protocol (ICMP)

Is used to report errors and send messages about the delivery of a packet. It can also be used to test and troubleshoot connectivity issues on IP networks. ________ messages are generated under error conditions in most types of unicast traffic, but not for broadcast or multicast packets. An ______ message is encapsulated within a single IP packet. ICMP messages are categorized into various types.

Hop

One link in the path from a host to a router or from router to router. Each time a packet passes through a router, its _____ count (or TTL) is decreased by one.

Reverse ARP (RARP)

One of the first autoconfiguration mechanisms. This allows a host to obtain an IP address from a server configured with a list of MAC:IP address mappings. _____ can be used to obtain only an IP address, which is inadequate for most implementations of IP.

Loopback address

Range 127.0.0.0 to 127.255.255.255 is reserved. This is a special address typically used to check that TCP/IP is correctly installed on the local host. The _______ interface does not require a physical interface to function. A packet sent to a _______ is not processed by a network adapter, but is otherwise processed as normal by the host's TCP/IP stack.

Dynamic routing protocol

Routes to other IP networks can be manually configured or learned by a ___________.

Base

The ____ of any number system tells you two things: how many different values any given digit can have and the factor by which the value of a digit increases as you move from right to left in a number.

Classless addressing

The concept of address classes and default masks is abandoned in favor of representing the address with an appropriately sized network prefix. For example, when expressed in binary, the subnet mask 255.255.240.0 contains 20 ones followed by 12 zeroes. Therefore, the network prefix, expressed in slash notation, is 172.30.0.0/20.

255.0.0.0

The default subnet masks correspond to the three classes of unicast IP address (A, B, and C). The default masks comprise whole octets: Class A is _____________.

IP version 6 (IPv6)

provides a long-term solution to the problem of address space exhaustion. Its 128-bit addressing scheme has space for 340 undecillion unique addresses. Even though only a small part of the scheme can currently be allocated to hosts, there is still enough address space within that allocation for every person on the planet to own approximately 4,000 addresses. As well as coping with the growth in ordinary company networks and Internet access subscribers, it is designed to meet the demands of billions of handheld and personal devices with Internet connectivity.

Dynamic Host Configuration Protocol (DHCP)

provides an automatic method for allocating an IP address, subnet mask, and optional parameters, such as the Default gateway and DNS server addresses. ________ is defined in RFC 2131. All the major operating systems provide support for ______ clients and servers.

Automatic Private IP Addressing (APIPA)

was developed by Microsoft as a means for clients that could not contact a DHCP server to communicate on the local network anyway. If a Windows host does not receive a response to a DHCPDISCOVER broadcast within a given time frame, it randomly selects an address from the range 169.254.1.1 to 169.254.254.254. It then performs an ARP broadcast to check that the address is currently unused; if it is in use, the host selects another address, and repeats the broadcast, and so on.